Cushioning device for use with a pneumatic impact tool or the like

Abstract

A cushioning device for use with a pneumatic impact tool which utilizes a part of compressed air for driving the piston of the tool as cushioning means and is self controllable.

What is claimed is: 
     
       1. A cushioning device for a pneumatic impact tool or the like having an impact means such as a chisel and a housing means provided with first exhaust hole means opening to the atmosphere, said device comprising: a rear cylinder closed at its front and rear ends and having air inlet port means and air port means in communication with the interior of the cylinder;   a front cylinder interconnected concentrically with the rear cylinder and closed at its rear end by the closed front end of the rear cylinder, said rear and front cylinders being axially slidably mounted in said housing means;   a piston mounted in the front cylinder for reciprocal sliding movement between the front closed end of the rear cylinder and said impact means;   a first outer cylindrical sleeve mounted over and coaxilly with the rear cylinder and within the housing means, the sleeve including an air outlet port means opening to said air space and communicable with said air port means;   a second outer cylindrical sleeve mounted over and coaxially with the front cylinder, the second outer cylindrical sleeve having second exhaust hole means communicable with said first exhaust hole means; and   an air space defined at least in part by the end face of one of the rear cylinder and the front cylinder, a first outer cylindrical sleeve mounted over the rear cylinder, and a second cylindrical sleeve interposed between said cylinders and said housing means, said first outer cylindrical sleeve having air outlet port means opening to said air space and communicable with said air port means, said second cylindrical sleeve having second exhaust hole means communicable with said first exhaust hole means;   said first and second exhaust holes, said air inlet port means and said air outlet port means being arranged such that as the rear and front cylinders are moved backward due to reaction forces exerted on the piston when the impact means strikes a workpiece to reduce the volume of the air space, the air in the air space is initially discharged through the second and first exhaust hole means to the atmosphere until the second exhaust hole means is closed by the front cylinder whereafter the air pressure in the space is increased to cushion the rearward movement of the cylinders and such that continued rearward movement of the cylinders brings the air inlet port means into alignment with the air outlet port means to permit the air in the space to escape through the aligned port means into the interior of the rear cylinder so that the air in the space continues to perform the cushioning function in a self-controlled manner.   
     
     
       2. The cushioning device of claim 1 comprising in addition ball means disposed between the housing means and the cylinders to facilitate smooth axial movement of the cylinders while inhibiting circumferential movement of the cylinders with respect to the housing means. 
     
     
       3. A cushioning device for a pneumatic impact tool or the like comprising: a housing having substantially cylindrical symmetry;   a first cylinder mounted within and coaxial with the housing;   a second cylinder attached to the first cylinder and coaxial with the housing;   a piston mounted within the second cylinder and coaxial with the second cylinder;   means for admitting compressed air into a bore of the piston to drive the piston into motion toward an impact device;   first port means for venting compressed air from the bore into an enlarged bore to reduce driving force on the piston;   second port means for admitting compressed air into a space to move the piston backward;   third port means for discharging air from a space that surrounds the first cylinder and is compressed by backward movement of the first and second cylinders when the third port means is closed to provide a first level of cushioning; and   fourth port means for discharging a reduced volume of the compressed air in the space into an interior of the first cylinder to reduce pressure of the compressed air in the space to a lower value, thereby providing a second level of cushioning, and to vent the space to the atmosphere.